
Neuroanatomical Distribution of the Serotonergic System in the Brain and Retina of Holostean Fishes, The Sister Group to Teleosts
Author(s) -
Daniel Lozano,
Antonio Uriarte González,
Jesús M. López
Publication year - 2020
Publication title -
brain, behavior and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 77
eISSN - 1421-9743
pISSN - 0006-8977
DOI - 10.1159/000505473
Subject(s) - pretectal area , serotonergic , biology , retina , neuroscience , raphe nuclei , preoptic area , raphe , hypothalamus , central nervous system , anatomy , serotonin , midbrain , biochemistry , receptor
Among actinopterygian fishes, holosteans are the phylogenetically closest group to teleosts but they have been much less studied, particularly regarding the neurochemical features of their central nervous system. The serotonergic system is one of the most important and conserved systems of neurotransmission in all vertebrates. By means of immunohistochemistry against serotonin (5-hydroxytryptamine), we have conducted a comprehensive and complete description of this system in the brain and retina of representative species of the 3 genera of holostean fishes, belonging to the only 2 extant orders, Amiiformes and Lepisosteiformes. Serotonin-immunoreactive cell groups were detected in the preoptic area, the hypothalamic paraventricular organ, the epiphysis, the pretectal region, the long and continuous column of the raphe, the spinal cord, and the inner nuclear layer of the retina. Specifically, the serotonergic cell groups in the preoptic area, the epiphysis, the pretectum, and the retina had never been identified in previous studies in this group of fishes. Widespread serotonergic innervation was observed in all main brain regions, but more abundantly in the subpallium, the hypothalamus, the habenula, the optic tectum, the so-called cerebellar nucleus, and the area postrema. The comparative analysis of these results with those in other groups of vertebrates reveals some extremely conserved features, such as the presence of serotonergic cells in the retina, the pineal organ, and the raphe column, while other characteristics, like the serotonergic populations in the preoptic area, the paraventricular organ, the pretectum, and the spinal cord are generally present in all fish groups, but have been lost in most amniotes.